THIS APPLICATION IS A U.S. NATIONAL PHASE APPLICATION OF PCT INTERNATIONAL APPLICATION PCT/JP99/06980.
The present invention relates to a multi-track disk reproducing apparatus that transfers data at a high speed by simultaneously reading a plurality of tracks.
Conventionally, as a means for increasing a data transfer rate of an optical disk system, a method (it is hereinafter called a multi-beam method) for simultaneously reproducing a plurality of tracks on an optical disk is suggested.
More specifically, this method is used to increase the data transfer rate in the following processes:
(1) A plurality of adjacent tracks are simultaneously read using an optical pickup constituted with plural pairs of light emitting elements and light receiving elements;
(2) The read data are stored in a buffer memory;
(3) The stored data are read out in the same order as the alignment of the tracks on the optical disk.
A conventional multi-beam method is hereinafter described in more details.
FIG. 1 is a block diagram of an optical disk reproducing apparatus for reproducing an optical disk in the conventional multi-beam method. This example shows an apparatus capable of simultaneously reading data on four tracks. The reproducing apparatus comprises the following elements:
(a) optical disk 1 on which tracks are formed concentrically or spirally,
(b) spindle motor 2 for supporting and rotating optical disk 1,
(c) light emitting elements 31, 32, 33, 34 for respectively radiating laser beams to four adjacent tracks on rotating optical disk 1,
(d) light receiving elements 41, 42, 43, 44 that receive reflected lights from respective irradiated tracks and convert them to electric signals,
(e) optical pickup 5 constituted with light emitting elements 31, 32, 33, 34 and light receiving elements 41, 42, 43, 44,
(f) feed motor 6 for moving optical pickup 5 radially of optical disk 1,
(g) reproducing circuits 71, 72, 73, 74 for respectively reproducing independent data read simultaneously from four tracks, based on electric signals supplied from optical pickup 5,
(h) memory control circuit 8 that temporarily stores the independent data reproduced by reproducing circuits 71, 72, 73, 74 in buffer memory 9, reads out the reproduced data stored in buffer memory 9 in the same order as the alignment of the tracks on optical disk 1, and transmits it to host interface 10,
(i) host interface 10 for receiving reproducing instructions or transmitting the reproduced data from/to a host device through terminal 11, and
(j) controller 12 for controlling the elements discussed above.
These elements are configured as shown in FIG. 1.
In this example, simultaneous reading of four tracks is usually allowed, but a reading error occurs in some compact diskxe2x80x94read only memory (CD-ROM) device. Recently, even an individual user has been able to write data onto a CD-ROM disk thanks to diffusion of a CD-R or the like, but disks are widespread which have extremely bad recording states depending on poor characteristic compatibility between a CD-R media and a CD-R drive, or recording speeds. On such CD-ROM device, error occurrence is hardly prevented even by a strong error-correcting-function of the CD-ROM. In addition, a reading error may occur because of a large flaw on the disk or a defect during its manufacture.
When such reading error occurs in a conventional CD-ROM device whose single track is read, generally, its head is immediately returned to the track having the error to try rereading, and the reproducing rate is simultaneously decreased to try reproduction. At this time, however, there is a problem that the reproduction is interrupted to extremely decrease the reading rate. In addition, the similar method is used even for a CD-ROM device whose plural tracks are reproduced simultaneously, and therefore, the similar problem occurs.
For resolving the conventional problem discussed above, a reading-error recovery method in accordance with the present invention has the following characteristics. First, among a plurality of reading means capable of simultaneously reading, the tailing reading means is used for rereading an error-occurrence-address, and the heading reading means continues to read data in an unread region. Next, when the rereading of the error-occurrence-address is completed, depending on number of unread tracks assigned to the plurality of reading means during the rereading of the error-occurrence-address and on an error occurrence position on the track, selective switching is performed between the following processes:
Track jump is carried out immediately and larger number of reading means are assigned to the unread tracks even during the rereading of the error-occurrence-address;
The tracks being read are continuously reproduced without performing any track-jump.
The present invention can restrain reduction of the reading rate to a minimum even when an error occurs and the rereading of the error-occurrence-address is tried.